a) Field of the Invention
The present invention relates to a relative velocity detecting apparatus for an automotive vehicle applicable to an automatic vehicular velocity control system which follows up a preceding vehicle which is running ahead of the vehicle on the same traffic lane if the preceding vehicle appears in a forward detection zone of the vehicle.
b) Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 6-187599 published on Jul. 8, 1994 exemplifies a previously proposed automotive vehicular radar apparatus which determines an inter-vehicle distance from a preceding vehicle to the vehicle using a laser beam radar unit as an inter-vehicle distance sensor.
In the previously proposed relative velocity detecting apparatus, the relative velocity vrn is calculated using a digital differentiation calculation according to the following equation (1) on the basis of inter-vehicle distance detection data dfn-1 and dfn through a predetermined filtering: EQU vrn=(dfn-1-dfn)/0.1[m/S] (1).
In the equation (1), 0.1 means a sampling time in seconds.